Samuel Brown, Francesco Martoni and Hamish Patrick have travelled to mountains, grasslands and forests - along the way cataloguing native weevils, psyllids, the picture wing fly and four new species of New Zealand's rare black mountain ringlet butterflies.

Mr Brown, who like his colleagues studies at Lincoln University's Bio-protection Research Centre, is specialising in weevils, which are commonly found in alpine areas in Canterbury and Otago.

Mr Brown said there were more than 60 species of weevil - some of which, like the clover root weevil, were costing the agriculture industry millions.

He said finding and understanding new species was no easy task, but it was an important step in knowing the impact they could have on the native environment.

"There's a lot of ground work that needs to be done. You need to understand what plant it feeds on, how long its lifecycle takes," he said.

"Does it have one generation a year? Does it have more than that? Does it have less than that? What predators attack it, what parasites might be controlling it, what disease it might have, what disease it might be spreading?

"There's a number of different factors that go into how problematic a species can be."

The European weevil was recently identified in New Zealand for the first time. Photo: Lincoln University